In recent years, along with higher performance and higher functionality in regard to digital apparatuses, increases in data transmission speeds and increases in bandwidth have been progressing quickly. To cope with this, standards for a high-speed data transmission beginning with an HDMI have been spreading quickly.
In addition, as represented by a portable apparatus, a mobile phone, an in-vehicle apparatus, or the like, the locations at which these apparatuses are used have increased regardless of being indoors or outdoors, and therefore higher reliability compared to the related art is required. However, in regard to a semiconductor component such as an IC (Integrated Circuit) and an LSI (Large Scale Integration), the miniaturization of circuits has proceeded year by year in order to realize miniaturization and a high-speed operation, and therefore resistance to static electricity entering from the outside is decreased. This has a significant effect regarding a decrease in the scale of embeddable protection elements, in addition to a decrease in the resistance property of the semiconductor itself.
In general, protection diodes are provided immediately after an input and output terminal of the LSI, and due to a function thereof, an internal circuit is protected from an external static pulse or the like. The protection diodes are instantly turned on when a voltage of a certain value or more is applied thereto and routes the current to a ground. When the protection diodes are connected in a multi-stage manner, the amount of current made to flow into the LSI is increased, and therefore, a predetermined resistance to electrostatic breakdown is secured. However, in terms of the configuration of these protection diodes, each of them maintains a capacitance component, such that the capacitance value becomes large when the protection diodes are connected in a multi-stage manner, and therefore this configuration has an adverse effect on a signal of a high-frequency band. Therefore, in the LSI used in a high-speed transmission line or the like, the protection elements that can be embedded are restricted, and accordingly, the resistance to the electrostatic breakdown is deteriorated.
As shown in FIG. 18, an electrostatic breakdown protection circuit 100 in the related art, which is used for these uses, includes a first transmission line 103 connected to a first input and output terminal 101, a second transmission line 104 connected to a second input and output terminal 102, a first ESD (ElectroStatic Discharge) protection element 105 connected between the first transmission line 103 and a ground, and a second ESD protection element 106 connected between the second transmission line 104 and a ground. A differential transmission circuit in the related art further includes a common mode filter 109 in which a first inductor element 107 serially connected between the first transmission 103 and a third transmission line 110 connected to a third input and output terminal 118, and a second inductor element 108 serially connected between the second transmission line 104 and a fourth transmission line connected to a fourth input and output terminal 119 are magnetically coupled to each other.
In this configuration, as the first and second ESD protection elements 105 and 106, an ESD suppressor or the like is used. The ESD suppressor has a low capacitance value of substantially 0.1 to 0.3 pF compared to, for example, a varistor, a zener diode, or the like, such that even when used in a high transmission line, the ESD suppressor does not disturb a defined characteristic impedance, and accordingly, it is possible to make the adverse effect on the signal of a high-frequency band as small as possible (for example, refer to PTL 1).